Fix error handling add error tests

Cython/Compiler/ExprNodes.py

@@ -4978,11 +4978,15 @@ class YieldExprNode(ExprNode):
     #
     # arg         ExprNode   the value to return from the generator
     # label_name  string     name of the C label used for this yield
+    # label_num   integer    yield label number
 
     subexprs = ['arg']
     type = py_object_type
+    label_num = 0
 
     def analyse_types(self, env):
+        if not self.label_num:
+            error(self.pos, "'yield' not supported here")
         self.is_temp = 1
         if self.arg is not None:
             self.arg.analyse_types(env)

Cython/Compiler/ParseTreeTransforms.py

@@ -1308,22 +1308,23 @@ class YieldNodeCollector(TreeVisitor):
     def __init__(self):
         super(YieldNodeCollector, self).__init__()
         self.yields = []
-        self.has_return = False
+        self.returns = []
+        self.has_return_value = False
 
     visit_Node = TreeVisitor.visitchildren
 
     def visit_YieldExprNode(self, node):
-        if self.has_return:
+        if self.has_return_value:
             error(node.pos, "'yield' outside function")
-        else:
         self.yields.append(node)
         node.label_num = len(self.yields)
 
     def visit_ReturnStatNode(self, node):
+        if node.value:
+            self.has_return_value = True
             if self.yields:
-            error(collector.returns[0].pos, "'return' with argument inside generator")
-        else:
-            self.has_return = True
+                error(node.pos, "'return' with argument inside generator")
+        self.returns.append(node)
 
     def visit_ClassDefNode(self, node):
         pass
@@ -1348,6 +1349,8 @@ class MarkClosureVisitor(CythonTransform):
         collector.visitchildren(node)
 
         if collector.yields:
+            if collector.returns and not collector.has_return_value:
+                error(collector.returns[0].pos, "'return' inside generators not yet supported ")
             node.is_generator = True
             node.needs_closure = True
             node.yields = collector.yields

tests/errors/e_generators.pyx

+def foo():
+    yield
+    return 0
+
+def bar(a):
+    return 0
+    yield
+
+def xxx():
+    yield
+    return
+
+yield
+
+class Foo:
+    yield
+
+_ERRORS = u"""
+3:4: 'return' with argument inside generator
+7:4: 'yield' outside function
+11:4: 'return' inside generators not yet supported
+13:0: 'yield' not supported here
+16:4: 'yield' not supported here
+"""